Patent GB-834115-A (GB)
Title: Improvements in method and apparatus for shaping and curing rubberized fabric articles
IPC: B29C35/00
Filed: 1957-12-03
Abstract: 834,115. Moulding air-springs. FIRESTONE TIRE & RUBBER CO. Dec. 3, 1957 [Dec. 11, 1956], No. 37620/57. Class 87(2). [Also in Group XXXII] Air spring bellows for vehicle suspension systems (see Group XXXII) are shaped and cured by a method in which a tubular blank is positioned within a mould, fluid is introduced under pulsating pressure to distend the blank within the forming surface of the mould and the blank is then subjected to increased pressure at an elevated temperature and cured in the mould in its distended condition. The blank, Fig. 2, comprising rubberised fabric plies 12, 13 and a rubber lining 14, with their ends wrapped round steel wire to form larger and smaller beads 15, 16, is placed in a lower mould section 34, Fig. 1, with the larger bead 15 secured thereto, a middle mould section 28 being swung out of the way (its bracket 29 pivoting on a vertical rod 30) for the purpose. A control valve 43 is opened and admits compressed air from a line 50 to the lower end of a cylinder 40, the piston-rod 39 of which rises and imparts a closing movement to the three mould sections 34, 28, 25. A projection 48 from the lower mould section 34 closes a limit switch 45 and a time control device 60 is set in operation, three control valves 63, 64, 65 then operating in timed sequence. The valve 63 opens and passes air to a solenoid-operated valve 58, controlling a threeway valve 55, and closes a pressure switch 66 which starts another timer 70. The timer 70 alternately energises and de-energises the solenoid valve 58, which when energised opens to direct air from a reservoir 52, at comparatively low pressure, through a line 57 to an insulated flexible mould supply line 37, and which when de-energised closes the line and opens to atmosphere, allowing the pressure in the line 37 to fall, the alternating operation thus producing a pulsating air pressure which progressively distends the blank into contact with the forming surfaces of the mould as the three sections close together. The angular relation of the crossed cords in the fabric plies is thus changed and stabilised in stages, avoiding distortion of the outer surface of the moulded article. Admission of pulsating air pressure inside the blank before the mould is fully closed is possible because the bead 16 is fitted with a closure disc 19, Fig. 3. The duration and frequency of the pulsating air pressure are controlled by the timer 70 suitably to the blank, as shown by a numerical example in the Specification. When the mould is fully closed a member 49 on the middle section 28 closes a limit switch 46, whereupon the valve 64 in the timer 60 opens and the valve 63 closes. The valve 64 opens a pressure valve 72, which stops and resets the timer 70, and operates a three-way valve 67 to close the line 57 and admit steam, at comparatively high pressure, from a line 68 to the mould supply line 37. At the end of the curing period the timer valve 65 is opened so as to reverse the control valve 43, opening at the mould sections. The supply line 37 communicates with the interior of the blank in the mould through conventional passages, not shown, and the mould is steam-jacketed, the steam being supplied from a header 44 and exhausted through a manifold 44A.